Control moment gyroscopes (CMGs) are commonly employed in satellite attitude control systems. A generalized CMG may include a main CMG housing and an inner gimbal assembly (IGA), which is mounted within the main CMG housing for rotation about a gimbal axis. The IGA includes, amongst other components, a rotor assembly, a spin motor, and a rotor housing. The rotor assembly includes a rotor rim, which may be disposed between first and second hemi-spherical rotor shell pieces. The rotor rim is welded to the first and second rotor shell pieces along first and second circumferential rim-shell weld joints, respectively. Collectively, the rotor rim, the first rotor shell piece, and the second rotor shell piece form a generally spherical body through which a rotor shaft is disposed. Opposing ends of the rotor shaft are each received by a spin bearing mounted within an annulus provided within the rotor housing. During operation, the spin motor rotates the rotor assembly about a spin axis at a relatively high rate of speed. The IGA is, in turn, selectively rotated about the gimbal axis, which is generally perpendicular to the rotor spin axis, by an actuator (e.g., a torque module assembly) mounted within the main CMG housing. When the IGA is “gimbaled” in this manner, a controlled torque is generated about an output axis normal to the spin and gimbal axes due to the mass and the rotational rate of the rotor assembly and, in particular, of the rotor rim. This generated torque is imparted to the host satellite through the CMG mount interface (e.g., an annular flange bolted to a mounting surface provided on the exterior of the satellite). Thus, by selectively rotating the IGA about the gimbal axis, the satellite's attitude may be adjusted as desired.
Traditionally, weight has been a primary driver in CMG design. However, as CMG weight has been continually reduced, a certain emphasis has shifted to the development of CMGs capable of achieving relatively high inertial levels within a streamlined (low volume) CMG envelope. Limitations associated with conventional rotor assemblies have hindered the development of such high inertia, low volume CMGs. As a key limitation, conventional rotor assemblies are generally unable to withstand the significant rotational speeds, sometimes exceeding 10,000 revolutions per minute, required to achieve the desired momentum levels while maintaining adequate structural integrity. This is due, in large part, to the significant mechanical stress experienced by the rotor assembly's rim-shell weld joints during high speed operation of the CMG.
Considering the above, it would be desirable to provide a rotor assembly for deployment within the inner gimbal assembly of a control moment gyroscope that maintains its structural integrity at high rotational speeds by reducing or redirecting the mechanical stress experienced by the rim-shell weld joints. Preferably, embodiments of such a rotor assembly would have a relatively streamlined (low volume) envelope. Other desirable features and characteristics of the present invention will become apparent from the subsequent Detailed Description and the appended claims, taken in conjunction with the accompanying drawings and this Background.